Select the correct option based on statements below:

Assertion (A): The stability of a crystal is reflected by the magnitude of its melting point.
Reason (R): Greater the intermolecular forces of attraction, the higher will be the stability and melting point of the substance.
 
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true but (R) is false.
4. Both (A) and (R) are false.
Subtopic:  Introduction & Crystal System |
 87%
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The packing efficiency of the face-centered cubic unit cell is:
(assuming that the atoms are touching each other)

1. 52.40 %

2. 68.04 %

3. 74 %

4. 79.06 %

Subtopic:  Density & Packing Fraction |
 85%
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Silver crystallizes in fcc lattice. If the edge length of the cell is 4.07 × 10−8 cm and density is 10.5 g cm−3, the atomic mass of silver is -

1. 120.31 g mol-1

2. 107.9 g mol-1

3. 207.60 g mol-1

4. 138.52 g mol-1

Subtopic:  Density & Packing Fraction |
 81%
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Copper crystallizes into an fcc lattice with an edge length of 3.61 × 10−8 cm. The density of copper crystal will be - 

1. 7.46 g cm-3

2. 9.67 g cm-3

3. 8.96 g cm-3

4. 5.63 g cm-3

Subtopic:  Density & Packing Fraction |
 50%
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Nickel oxide has the formula Ni0.98O1.00. The fraction of nickel existing as Ni3+ ions will be -

1. 0.041

2.  0.959

3. 0.736 

4. 0.264 

 

Subtopic:  Imperfections in Solids & Semiconductors |
 65%
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A ferric oxide crystallizes in a hexagonal close-packed array of oxide ions with two out of every three octahedral holes occupied by ferric ions. The formula of the ferric oxide is-

1. FeO

2. Fe2O3

3. Fe3O4

4. Fe3O2

Subtopic:  Voids, Radius Ratio & Coordination Number |
 72%
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A compound forms a hexagonal close-packed structure. The total number of voids in 0.5 moles

of the compound will be -

1. 9.033 × 1023
2. 3.011 × 1023
3. 6.023 × 1023
4. 8.024 × 1023

Subtopic:  Voids, Radius Ratio & Coordination Number |
 53%
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A compound is formed by two elements M and N. The element N forms ccp and atoms of M occupy 1/3rd of tetrahedral voids. The formula of the compound would be -

1. MN

2. M3N4

3. M2N3

4. M3N2

Subtopic:  Voids, Radius Ratio & Coordination Number |
 76%
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An element with a molar mass of 2.7 × 10-2 kg mol-1  and density  2.7 × 103 kg m-3  forms a unit cell with an edge length of 405 pm. The type of unit cell is-

1. Simple cubic cell.

2. Face-centered cubic cell.

3. Body-centered cubic cell.

4. None of the above.

Subtopic:  Density & Packing Fraction |
 77%
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 The pair having only molecular solids among the following is -

1. Brass and SiC

2. Ammonium phosphate (NH4)3PO4

3. SiC and plastic 

4. Tetra phosphorus decaoxide (P4O10) and I2

Subtopic:  Introduction & Crystal System |
 67%
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